The present invention relates generally to improvements in weaving and weaving machines. More particularly, the present invention relates to a method of inserting different weft threads having different yarn properties into the warp shed of an air jet weaving machine according to a predetermined insertion pattern or sequence. The different weft threads are fed from corresponding spools to a first jet arrangement supplied with a flowing fluid. The weft threads are inserted into the warp shed through the first jet arrangement and a second jet arrangement downstream of the first jet arrangement in the weft insertion direction. The second jet arrangement is also supplied with a flowing fluid.
In the previous insertion methods which are widely known and used on numerous commercially available air jet weaving machines, different types of weft threads are generally not transported in the identical manner by the flowing fluid. The differences in the weft threads may be differences in such characteristics as the material, the thickness, the color, or the surface properties. Differences in thread properties can affect, e.g., the energy transfer of the flowing fluid to the weft thread. For example, fuzzy threads provide better energy transfer than smooth threads. In order to ensure that the less easily transported threads are inserted within the time period available for weft insertion (according to the known methods), the fluid is supplied to the first jet arrangement at a higher pressure for these weft threads than for more easily transported weft threads. At the same time, the fluid supply pressure at the second jet arrangement is kept the same for all types of weft threads.
Since the fluid supply pressure at the first jet arrangement may be increased only within the limited range below the point at which the given thread is damaged, it has not been possible previously to employ certain combinations of widely differing yarns. Attempts to do so have led to weaving faults (due to a too low pressure used with a less easily transported weft thread) or to damage of the weft thread (due to a too high pressure). Also, the known technique of keeping the pressure at the second jet arrangement constant has been detrimental. When the pressure is too low, a less easily transported weft thread is inserted, and held after insertion, in a too slack condition. Further, when the pressure is too high, a weft thread which is sensitive to being damaged, e.g., a slightly twisted yarn, may suffer damage. With a slightly twisted yarn, unraveling of the leading end of the yarn by the action of the fluid may occur.
It is therefore an object of the present invention to improve the known insertion method such that different weft thread types may be inserted in combinations not heretofore possible, without leading to problems (i.e., operating problems) or to faults.
This object and others are achieved according to the present invention by the following technique. The fluid supply pressure for at least a portion of the second jet arrangement is changed for different types of weft thread, synchronously with the insertion sequence.
Nearly all types of weft threads may be combined and inserted without difficulties when the method according to the present invention is employed. The beneficial effects of the technique of the present invention extend beyond the direct effect of the second jet arrangement on the transporting and tensioning and/or holding taut of the weft thread. There is also an indirect effect on the first jet arrangement, in that the range of fluid supply pressures needed for proper adjustment of the first jet arrangement is less when the fluid supply pressure at the second jet arrangement is optimized in the present invention.
The present invention further relates to a jet weaving machine for inserting various types of weft threads having different yarn properties in a predetermined repeated insertion sequence. The machine comprises a first jet arrangement disposed upstream of the warp shed in the weft insertion direction and a second jet arrangement disposed downstream of the first (in the weft insertion direction) and connected to a source of pressurized fluid via a supply line. The supply line includes a controlled valve. Also, a weft preparation device is disposed upstream of the first jet arrangement in the weft insertion direction. Also, a control arrangement for controlling the feed sequence of the different weft threads from the weft preparation device to the first jet arrangement is provided.
The inventive jet weaving machine according to the present invention further includes a controlled adjusting means provided in connection with at least a portion of the second jet arrangement. In this way, the fluid supply pressure at the portion is adjustable to different values corresponding to different threads in the insertion sequence.
According to a further aspect of the present invention, the controlled adjusting means are connected to and controlled by the control arrangement which controls the feed sequence of the weft threads.
In a first embodiment of the inventive jet weaving machine, the fluid supply line for the second jet arrangement includes a first closing valve which is operated synchronously with the weft insertion cycle and sequence. The fluid supply line further includes a first pressure-reducing valve. At least one auxiliary supply line is included in the controlled adjusting means, which auxiliary line connects the source of the pressurized fluid to a segment of the main fluid supply line lying between the first reducing valve and the first closing valve. The auxiliary line includes a second closing valve and a second pressure-reducing valve. The second pressure reducing valve is set at a higher pressure than the first reducing valve, and the second closing valve is opened by the control arrangement which controls the feed sequence of the weft threads. The opening of the second closing valve occurs only during the insertion phase of the weft threads having yarn properties which require a higher fluid supply pressure.
In a second embodiment of the inventive jet weaving machine, the fluid supply line for the second jet arrangement includes a first closing valve and a first pressure-reducing valve. At least one second supply line connects the source of the pressurized fluid to the second jet arrangement, which second supply line includes a second closing valve and a second pressure-reducing valve. Both closing valves are connected to the control arrangement which controls the feed sequence of the weft threads and are selectively actuable corresponding to different threads in the insertion sequence.